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Show 712 MR. T. MANNERS-SMITH ON THE [DeC. 4, Sacred Plexus. The nerves entering into this plexus are a large part of the first lumbar, the whole of the second lumbar, and the whole of the first sacral. Portion derived from lumbar nerves divides into two branches ; the first sacral also divides into two branches. One of the branches from lumbar part of plexus fuses with one of the branches from sacral part of plexus and forms the peroneal nerve ; this, as it passes down the leg, divides into two branches, which seem to represent peroneal and external plantar. Peroneal divides into a muscular branch passing to muscles mentioned in text and a cutaneous branch to the dorsum. The external plantar divides into a cutaneous branch to outer side of foot, and supplies certain muscles of the sole. The remaining branch from lumbar part of plexus unites with remaining branch from sacral part, and forms the internal popliteal nerve ; this divides into three branches: two lateral, to the inner and outer heads of the gastrocnemius; one to outer head supplying flexor longus digitorum in addition ; one to inner head supplying soleus and tibialis posticus. The continuation of the trunk passes doAvn and becomes the internal plantar, which is mainly cutaneous. A NOTE ON THE ARTERIAL SYSTEM. The arch of the aorta has the usual mammalian arrangement, turning to the left side. It gives off the three large cervical and brachial branches in the usual order, viz. innominate, left carotid, left subclavian. The trunk aorta passes down to the nineteenth vertebra (last lumbar), where it ends by dividing in a peculiar tree-like manner into three small and exceedingly short trunks on each side and a median caudal continuation of the vessel itself-thus there are seven trunks in all. Passing from Avithout inwards, the outermost of the three trunks divides almost immediately into the folloAving branches:- A small outermost branch for the region of the crest of the ilium. A large branch which passes beneath the psoas parvus and divides here into three branches, Avhich, running doAvn parallel to each other, are all distributed to the deep part of the front of the thigh, as seen in the diagram. A fairly large branch which soon divides into three, two passing to the superficial part of the front of the thigh, the remaining branch to the abdominal wall. These arteries pass over the psoas parvus ; they may represent superficial femoral and epigastric. The last branch from the outermost trunk is a vessel which is partly distributed to abdominal wall and also gives off branches which descend into pelvis, together with two obturator arteries-large and small. The second trunk division of the abdominal aorta: this 2nd division corresponds in its distribution with Hyrtl's* internal iliac, 1 Denkschriften Wiener Akademie, Bd. v. |
